Fixed. It wasn't what I thought. I had made changes in the way upload files were read and had neglected to account for every possible situation. All TRP Sieve workunits have been revalidated and there aren't any of them with validate errors any more. A validate error generally means that there's something wrong with the result itself. In this case the uploads were not being read at all and the validator considered them to be missing.
Thank you, Patrick, for pointing that out.